GI regulatory substances Flashcards
cholecystokinin: source, action, regulation, mechanism
source: I cells of the jejunum and ileum
action: increase pancreatic and gall bladder secretion, increase relaxation at the sphincter of Oddi, decrease gastric emptying
regulation: increased by fatty acids, amino acids
mechanism: acts on neural muscarininc pathways to cause pancreatic secretion
gastrin: source, action, regulation
source: G cells (antrum of stomach)
action: increase gastric acid production, increase gastric motility, increase growth of gastric mucosa
regulation: increased by stomach distension, alkalization, aminoa acids, peptides, and vagal stimulation
decreased by stomach pH under 1.5
Under what conditions does gastrin production increase?
a LOT with zollinger-ellison sydrome
a little with chronic proton pump inhibitor use
What are potent stimulators of gastrin
phenylalanine and tryptophan
GIP: source, action, regulation
aka glucose-dependent insulinotropic peptide
source: K cells in the jejunum and ileum
action: increase insulin secretion; decrease gastric acid secretion
regulation: increased by fatty acids, amino acids, oral glucose
Implications of GIP secretion for IV nutrition
oral glucose load is used more rapidly than the equivalent load given by IV
Motilin: source, action, regulation
source: small intestine
action: produces migrating motor complexes
regulation: increased in fasting state
What is a drug tie-in for motilin
motilin receptor agonists like erythromycin are used tostimulate intestinal peristalsis
secretin: source, action, regulation
source: S cells in the duodenum
action: increase pancreatic HCO3- secretion, decrease gastric acid secretion, increase bile secretion
incr. by acid, fatty acids in the lumen of the duodenum. this is important- neutralizing gastric acids allows pancreatic enzymes to function
somatostatin: source, action, regulation
source: D cells of the pancreatic islets, GI mucosa
action: inhibitory action. decrease gastric acid and pepsinogen secretion, decrease pancreatic and small intestine fluid secretion, decrease gall bladder contraction, decrease insulin and glucugon release
regulation: increased by acid, decreased by vagal stim
What is the action of nitric oxide in the GI system, and what is an example of its relevance to disease
NO: relaxes smooth musches, including LES
loss of NO secretion is implicated in increased LES tone in achalasia
Vasoactive intestinal peptide: source, action, regulation
source: parasympathetic ganglia in sphincters, gallbladder, and small intestine
action: increase intestinal water and electrolye secretion
increase relaxation of intestinal smooth muscle and sphincters
regulation: increased by distension and vagal stimulation
decreased by adrenergic input
What is a VIPoma?
tumor non-alpha, non-beta pancreatic islet cells. causes watery diarrhea, hypokalemia, and achlorhydria (no stomach acid secretion)
What regulatory substance of the GI tract has antigrowth hormone effects?
somatostatin (inhibits digestion and absorption of substances needed for growth)
